Use of substitute 2,4-bis (alkylamino) pyrimidines or quinzolines as antimicrobials

ABSTRACT

The use of 2,4—bis(alkylamino)pyrimidines of formula (1) R 1  is C 1 -C 12 alkyl or C 6 -C 10 laryl; R 2  is hydrogen or C 1 -C 12 alkyl; or R 1  and R 2  together form a radical of formula (1 a ) R′ and R″ are each independently of the other hydrogen, C 1 -C 6 alkyl or C 1 -C 6 alkoxy, R 3  and R 5  are each independently of the other hydrogen or C 1 -C 8 alkyl; R 4  is C 1 -C 20 alkyl, unsubstituted phenyl, C 6 -C 10 aryl, C 6 -C 10 aryl-C 1 -C 6 alkyl, hydroxy-C 1 -C 6 alkyl, di-C 1 -C 6 alkylamino-C  1 -C 6 alkyl, mono-C 1 -C 6 alkylamino-C 1 -C 6 alkyl, —(CH 2 )2-(O—(CH 2 ) 2 ) 1-4 —OH or —(CH 2 ) 2 —(O—(CH 2 ) 2 ) 1-4 —NH 2 ; R 6  is C 1 -C 20 alkyl, C 6 -C 10 aryl, C 6 -C 10 aryl-C 1 -C 6 alkyl, hydroxy-C 1 -C 6 alkyl, di-C 1 C 6 alkylamino-C 1 -C 6 alkyl, mono- C 1 -C 6 alkylamino-C 1 -C  6 alkyl, —(CH 2 ) 2 —(O—(CH 2 ) 2 ) 1-4 —OH or —(CH 2 ) 2 —(O—(CH 2 ) 2 ) 1-4 —NH 2 ; or R 3  and R  4  and/or R 5  and R 6 , together form a pyrrolidine, piperidine, hexamethyleneimine or morpholine ring; in the antimicrobial treatment of surfaces.

The present invention relates to the use of substituted 2,4-bis(alkylamino)pyrimidines in the antimicrobial treatment of surfaces and to the preparation of such compounds.

The present invention relates to the use of 2,4-bis(alkylamino)pyrimidines of formula

wherein

-   R₁ is C₁-C₁₂alkyl or C₆-C₁₀aryl; -   R₂ is hydrogen or C₁-C₁₂alkyl; or R₁ and R₂ together form a radical     of formula

wherein

-   R′ and R′″ are each independently of the other hydrogen, C₁-C₆alkyl     or C₁-C₆alkoxy; -   R₃ and R₅ are each independently of the other hydrogen or     C₁-C₈alkyl; -   R₄ is C₁-C₂₀alkyl, unsubstituted phenyl, C₆-C₁₀aryl, preferred     C₇-C₁₀aryl; C₆-C₁₀aryl-C₁-C₈alkyl, hydroxy-C₁-C₆alkyl,     di-C₁-C₆alkylamino-C₁-C₆alkyl, mono-C₁-C₆alkylamino-C₁-C₈alkyl,     —(CH₂)₂(O—(CH₂)₂)₁₋₄—OH or —(CH₂)₂—(O—(CH₂)₂)₁₋₄—NH₂; -   R₆ is C₁-C₂₀alkyl, C₈-C₁₀aryl, C₆-C₁₀aryl-C₁-C₈alkyl,     hydroxy-C₁-Calkyl, di-C₁-C₈alkylamino-C₁-Calkyl,     mono-C₁-C₆alkylamino-C₁-C₆alkyl, —(CH₂)₂—(O—(CH₂)₂)₁₋₄—OH or     —(CH₂)₂—(O—(CH₂)₂)₁₋₄—NH₂; or -   R₃ and R₄ and/or R₅ and R₆ together form a pyrrolidine, piperidine,     hexamethyleneimine or morpholine ring;     in the antimicrobial treatment of surfaces. -   C₁-C₂₀Alkyl is straight-chain or branched alkyl, e.g. methyl, ethyl,     n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, isoamyl     or tert-amyl, hexyl, isohexyl, heptyl, octyl, isooctyl, nonyl,     decyl, undecyl, dodecyl, tetradecyl, pentadecyl, hexadecyl,     heptadecyl, octadecyl or eicosyl. -   C₁-C₁₂Alkyl is straight-chain or branched alkyl, e.g. methyl, ethyl,     n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, isoamyl     or tert-amyl, hexyl, isohexyl, heptyl, octyl, isooctyl, nonyl,     decyl, undecyl or dodecyl. -   C₁-C₆Alkyl is straight-chain or branched alkyl, e.g. methyl, ethyl,     n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, isoamyl     or tert-amyl, isohexyl, hexyl, heptyl, octyl or isooctyl. -   C₁-C₄Alkyl is straight-chain or branched alkyl, e.g. methyl, ethyl,     n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl.

C₁-C₈Alkyl is straight-chain or branched alkyl, e.g. n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, isoamyl or tert-amyl, isohexyl, hexyl, heptyl, octyl or isooctyl, especially hexyl.

-   C₁-C₆Alkyl is straight-chain or branched alkyl, e.g. methyl, ethyl,     n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl, isoamyl     or tert-amyl, hexyl or isohexyl. -   C₁-C₆Alkoxy is a straight-chain or branched radical, e.g. methoxy,     ethoxy, propoxy, butoxy, pentyloxy or hexyloxy. -   C₆-C₁₀Aryl denotes naphthyl and especially phenyl. C₆-C₁₀Aryl     radicals may be unsubstituted or may carry one or more, for example     one, two, three or four, identical or different substituents, which     may be in any desired position(s). Examples of such substituents are     C₁-C₄alkyl, halogen, hydroxy, C₁-C₄alkoxy, trifluoromethyl, cyano,     hydroxycarbonyl, C₁-C₄-alkoxycarbonyl, aminocarbonyl, amino,     C₁-C₄alkylamino, di-C₁-C₄alkylamino and C₁-C₄-alkylcarbonylamino.

Special preference is given to compounds of formula (1) wherein

-   R₁ is C₁-C₈alkyl or phenyl;     or to compounds of formula (1) wherein -   R₂ is hydrogen or C₃-C₈alkyl;     or to compounds of formula (1) wherein -   R₃ and R₅ are each independently of the other hydrogen or     C₁-C₈alkyl;     or to compounds of formula (1) wherein -   R₄ is C₁-C₁₂alkyl, unsubstituted phenyl, C₆-C₁₀aryl-C₁-C₆alkyl,     hydroxy-C₂-C₆alkyl, di-C₁-C₄-alkylamino-C₁-C₄alkyl,     mono-C₁-C₄alkylamino-C₁-C₄alkyl, —(CH₂)₂—(O—(CH₂)₂)_(1,2)—OH or     —(CH₂)₂—(O—(CH₂)₂)_(1,2)—NH₂; and -   R₆ is C₁-C₁₂alkyl, C₆-C₁₀aryl, C₆-C₁₀aryl-C₁-C₆alkyl,     hydroxy-C₂-C₆alkyl, di-C₁-C₄alkylamino-C₁-C₄alkyl,     mono-C₁-C₄alkylamino-C₁-C₄alkyl, —(CH₂)₂—(O—(CH₂)₂₎ _(1,2)—OH or     —(CH₂)₂—(O—(CH₂)₂)_(1,2)—NH₂;     or to compounds of formula (1) wherein -   R₃ and R₄ and/or R₆ and R₆ together form a pyrrolidine, piperidine,     hexamethyleneimine or morpholine ring.

Preference is given to the use according to the invention of compounds of formula

wherein

-   R′ is hydrogen, C₁-C₃alkyl or C₁-C₃alkoxy; -   R″ is C₁-C₃alkyl or C₁-C₃alkoxy; -   R₃ and R₅ are each independently of the other hydrogen or     C₁-C₈alkyl; and -   R₄ and R₆ are each independently of the other C₁-C₁₂alkyl,     phenyl-C₁-C₃alkyl, hydroxy-C₁-C₆-alkyl or     di-C₁-C₆alkylamino-C₁-C₆alkyl, mono-C₁-C₆alkylamino-C₁-C₆alkyl,     —(CH₂)₂—(O—(CH₂)₂)₁₋₄—OH or —(CH₂)₂—(O—(CH₂)₂)₁₋₄—NH₂; or -   R₃ and R₄ and/or R₅ and R₆ together form a pyrrolidine, piperidine,     hexamethyleneimine or morpholine ring.

Special preference is given to the use of compounds of formula (1) wherein

-   R₁ is C₁-C₈ or phenyl; -   R₂ is hydrogen or hexyl; or R₁ and R₂ together form a radical of     formula (1 a) wherein -   R′ is hydrogen, C₁-C₃alkyl or C₁-C₃alkoxy, and -   R″ is C₁-C₃alkyl or C₁-C₃alkoxy; -   R₃ and R₅ are each independently of the other hydrogen or     C₁-C₈alkyl; -   R₄ is C₁-C₁₂alkyl, unsubstituted phenyl, C₆-C₁₀aryl-C₁-C₆alkyl,     hydroxy-C₂-C₆alkyl, di-C₁-C₄-alkylamino-C ₁-C₄alkyl,     mono-C₁-C₄alkylamino-C₁-C₄alkyl, —(CH₂)₂—(O—(CH₂)₂)_(1,2)—OH or     —(CH₂)₂—(O—(CH₂)₂)_(1,2)—NH₂; and -   R₆ is C₁-C₁₂alkyl, C₆-C₁₀aryl, C₆-C₁₀aryl-C₁-C₆alkyl,     hydroxy-C₂C₆alkyl, di-C₁-C₄alkyl-amino-C₁-C₄alkyl,     mono-C₁-C₄alkylamino-C₁-C₄alkyl, —(CH₂)₂—(O—(CH₂)₂)_(1,2)—OH or     —(CH₂)₂—(O—CH₂)₂)_(1,2)—NH₂; or -   R₃ and R₄ together, and R₅ and R₆ together, form a pyrrolidine,     piperidine, hexamethyleneimine or morpholine ring.

There are used especially compounds of formula (1) wherein R₃ and R₅, and R₄ and R₆, have the same meanings.

Especially preferred compounds are those of the following formulae

Examples of compounds used according to the invention are listed in Table 1:

TABLE 1 Compound Purity Purity of formula Structure Mass GC (%) LC (%) PY1 

400  25 (GC) PY2 

473  80 (GC) PY3 

385  78 (GC) PY4 

356 100 (GC) PY5 

349 98 (GC) PY6 

461  35 (GC) PY7 

292 100 (GC) PY8 

304 100 (GC) PY9 

332 100 (GC) PY10

339 97 (LC) PY11

375 50 (LC) Py12

398 70 (LC) PY13

341 94 (LC) PY14

397 90 (LC) PY15

282 96 (LC) PY16

318 82 (LC) PY17

341 60 (LC) PY18

312 98 (LC) PY19

369 84 (LC) PY20

290 97 (LC) PY21

312 85 (LC) PY22

352 89 (LC) PY23

376 96 (LC) PY24

290 99 (LC) PY25

292 92 (LC) PY26

349 88 (LC) PY27

292 93 (LC) PY28

264 77 (LC) PY29

321 93 (LC) PY30

433 68 PY31

375 97 PY32

411 26 PY33

434 58 PY34

377 84 PY35

433 77 PY36

319 99 PY37

355 77 PY38

378 73 PY39

377 65 PY40

306 32 PY41

337 91 PY42

349 90 PY43

405 83 PY44

290 99 PY45

326 51 PY46

349 72 PY47

278 55 PY48

308 90 PY49

411 87 PY50

467 90 PY51

353 97 PY52

412 94 PY53

371 57 PY54

335 85 PY55

452 49 PY56

430 40 PY57

332 70 PY58

304 78 PY59

318 65 PY60

284 48 PY61

403 74 PY62

310 78 PY63

409 61 PY64

387 56 PY65

449 28 PY66

391 93 PY67

333 90 PY68

383 90 PY69

369 75 PY70

351 94 PY71

349 91 PY72

378 87 PY73

410 48 PY74

367 92

The compounds used according to the invention are prepared according to methods known per se. The substituted 2,4-bis(alkylamino)pyrimidines are obtained by reacting the corresponding dichloropyrimidine compound (formula (1b)) with a primary or secondary amine-depending upon the meanings of the radicals R₃ and R₅— in a suitable solvent, e.g. DMF, di-oxane, toluene, xylene, ethanol or butanol, and an auxiliary base, e.g. triethylamine, DIEA, sodium carbonate, potassium carbonate, etc., or using an excess of the amine compound, for a period of from 1 to 24 hours at 40-150° C. The reaction takes place according to the following Scheme (I):

or the compounds used according to the invention are prepared by condensing a guanidine compound with a suitable β-keto ester using an auxiliary base, e.g. sodium carbonate, potassium carbonate, sodium ethanolate, sodium methanolate or potassium tert-butanolate, in a suitable solvent, e.g. methanol, ethanol, butanol, tert-butanol, tetrahydrofuran, dimethylformamide, acetonitrile, toluene or xylene, for a period of from 1 hour to 24 hours at a temperature of from 40 to 150° C. The resulting 2-alkylamino-4-hydroxy-pyrimidine is then converted into the corresponding 2-alkylamino-4-chloro-pyrimidine compound according to customary methods by means of phosphorus oxychloride.

The substituted 2,4-alkylamino-pyrimidines are obtained by reacting the 2-alkylamino-4-chloro-pyrimidine compound with a primary or secondary amine (R₄R₅NH) in a suitable solvent, e.g. methanol, ethanol, butanol, tetrahydrofuran, dimethylformamide, dioxane, toluene or xylene, and an auxiliary base, e.g. triethylamine, DIEA, sodium carbonate, potassium carbonate or an excess of amine, for a period of from 1 to 24 hours at a temperature of from 40 to 150° C. The reaction takes place according to the following Scheme (II):

The 2,4-bis(alkylamino)pyrimidines used according to the invention exhibit a pronounced antimicrobial action, especially against pathogenic gram-positive and gram-negative bacteria and against bacteria of skin flora, and also against yeasts and moulds. They are therefore suitable especially in the disinfection, deodorisation and the general and antimicrobial treatment of the skin and mucosa and also of integumentary appendages (hair), more especially in the disinfection of the hands and of wounds.

They are therefore suitable as antimicrobial active ingredients and preservatives in personal care preparations, for example shampoos, bath additives, hair-care products, liquid and solid soaps (based on synthetic surfactants and salts of saturated and/or unsaturated fatty adds), lotions and creams, deodorants, other aqueous or alcoholic solutions, e.g. cleansing solutions for the skin, moist cleansing cloths, oils or powders.

The invention therefore relates also to a personal care preparation comprising at least one compound of formula (1) as well as cosmetically tolerable carriers or adjuvants. The personal care preparation according to the invention contains from 0.01 to 15% by weight, preferably from 0.1 to 10% by weight, based on the total weight of the composition, of a compound of formula (1) and cosmetically tolerable adjuvants.

Depending upon the form of the personal care preparation, it will comprise, in addition to the 2,4-bis(alkylamino)pyrimidine of formula (1), further constituents, for example sequestering agents, colourings, perfume oils, thickening or solidifying agents (consistency regulators), emollients, UV absorbers, skin-protective agents, antioxidants, additives that improve mechanical properties, such as dicarboxylic acids and/or Al, Zn, Ca and Mg salts of C₁₄-C₂₂ fatty acids, and optionally preservatives.

The personal care preparation according to the invention may be formulated as a water-in-oil or oil-in-water emulsion, as an alcoholic or alcohol-containing formulation, as a vesicular dispersion of an ionic or non-ionic amphiphilic lipid, as a gel, a solid stick or as an aerosol formulation.

As a water-in-oil or oil-in-water emulsion, the cosmetically tolerable adjuvant contains preferably from 5 to 50% of an oily phase, from 5 to 20% of an emulsifier and from 30 to 90% water. The oily phase may contain any oil suitable for cosmetic formulations, e.g. one or more hydrocarbon oils, a wax, a natural oil, a silicone oil, a fatty acid ester or a fatty alcohol. Preferred mono- or poly-ols are ethanol, isopropanol, propylene glycol, hexylene glycol, glycerol and sorbitol.

Cosmetic formulations according to the invention may be used in a variety of fields. Especially the following preparations, for example, come into consideration:

-   -   skin-care preparations, e.g. skin-washing and cleansing         preparations in the form of tablet-form or liquid soaps,         synthetic detergents or washing pastes;     -   bath preparations, e.g. liquid (foam baths, milks, shower         preparations) or solid bath preparations, e.g. bath cubes and         bath salts;     -   skin-care preparations, e.g. skin emulsions, multi-emulsions or         skin oils;     -   cosmetic personal care preparations, e.g. facial make-up in the         form of day creams or powder creams, face powder (loose or         pressed), rouge or cream make-up, eye-care preparations, e.g.         eyeshadow preparations, mascara, eyeliner, eye creams or eye-fix         creams; lip-care preparations, e.g. lipsticks, lip gloss, lip         contour pencils, nail-care preparations, such as nail varnish,         nail varnish removers, nail hardeners or cuticle removers;     -   intimate hygiene preparations, e.g. intimate washing lotions or         intimate sprays;     -   foot-care preparations, e.g. foot baths, foot powders, foot         creams or foot balsams, special deodorants and antiperspirants         or callus-removing preparations;     -   light-protective preparations, such as sun milks, lotions,         creams and oils, sun blocks or tropicals, pre-tanning         preparations or after-sun preparations;     -   skin-tanning preparations, e.g. self-tanning creams;     -   depigmenting preparations, e.g. preparations for bleaching the         skin or skin-lightening preparations;     -   insect-repellents, e.g. insect-repellent oils, lotions, sprays         or sticks;     -   deodorants, such as deodorant sprays, pump-action sprays,         deodorant gels, sticks or roll-ons;     -   antiperspirants, e.g. antiperspirant sticks, creams or roll-ons;     -   preparations for cleansing and caring for blemished skin, e.g.         synthetic detergents (solid or liquid), peeling or scrub         preparations or peeling masks;     -   hair-removal preparations in chemical form (depilation), e.g.         hair-removing powders, liquid hair-removing preparations, cream-         or paste-form hair-removing preparations, hair removing         preparations in gel form or aerosol foams;     -   shaving preparations, e.g. shaving soap, foaming shaving creams,         non-foaming shaving creams, foams and gels, preshave         preparations for dry shaving, aftershaves or after-shave         lotions;

fragrance preparations, e.g. fragrances (eau de Cologne, eau de toilette, eau de parfum, parfum de toilette, perfume), perfume oils or cream perfumes;

-   -   dental-care, denture-care and mouth-mare preparations, e.g.         toothpastes, gel toothpastes, tooth powders, mouthwash         concentrates, anti-plaque mouthwashes, denture cleaners or         denture fixatives;     -   cosmetic hair-treatment preparations, e.g. hair-washing         preparations in the form of shampoos and conditioners, hair-care         preparations, e.g. pretreatment preparations, hair tonics,         styling creams, styling gels, pomades, hair rinses, treatment         packs, intensive hair treatments, hair-structuring preparations,         e.g. hair-waving preparations for permanent waves (hot wave,         mild wave, cold wave), hair-straightening preparations, liquid         hair-setting preparations, hair foams, hairsprays, bleaching         preparations, e.g. hydrogen peroxide solutions, lightening         shampoos, bleaching creams, bleaching powders, bleaching pastes         or oils, temporary, semi-permanent or permanent hair colourants,         preparations containing self-oxidising dyes, or natural hair         colourants, such as henna or camomile.

An antimicrobial soap has, for example, the following composition:

-   0.01 to 5% by weight of a compound of formula (1) -   0.3 to 1% by weight titanium dioxide -   1 to 10% by weight stearic acid -   ad 100% soap base, e.g. the sodium salts of tallow fatty acid and     coconut fatty acid or glycerol.

A shampoo has, for example, the following composition:

-   0.01 to 5% by weight of a compound of formula (1) -   12.0% by weight sodium laureth-2-sulfate -   4.0% by weight cocamidopropyl betaine -   3.0% by weight NaCl and water ad 100%.

A deodorant has, for example, the following composition:

-   0.01 to 5% by weight of a compound of formula (1) -   60% by weight ethanol -   0.3% by weight perfume oil and water ad 100%.

The invention relates also to an oral composition containing from 0.01 to 15% by weight, based on the total weight of the composition, of a compound of formula (1) and orally tolerable adjuvants.

Example of an oral composition:

-   10% by weight sorbitol -   10% by weight glycerol -   15% by weight ethanol -   15% by weight propylene glycol -   0.5% by weight sodium lauryl sulfate -   0.25% by weight sodium methyloocyl taurate -   0.25% by weight polyoxypropylene/polyoxyethylene block copolymer -   0.10% by weight peppermint flavouring -   0.1 to 0.5% by weight of a compound of formula (1) and 48.6% by     weight water.

The oral composition according to the invention may be, for example, in the form of a gel, a paste, a cream or an aqueous preparation (mouthwash).

The oral composition according to the invention may also comprise compounds that release fluoride ions which are effective against the formation of caries, for example inorganic fluoride salts, e.g. sodium, potassium, ammonium or calcium fluoride, or organic fluoride salts, e.g. amine fluorides, which are known under the trade name Olafluor.

The 2,4-bis(alkylamino)pyrimidines of formula (1) used according to the invention are also suitable for the treatment, especially preservation, of textile fibre materials. Such materials are undyed and dyed or printed fibre materials, e.g. of silk, wool, polyamide or polyurethanes, and especially cellulosic fibre materials of all kinds. Such fibre materials are, for example, natural cellulose fibres, such as cotton, linen, jute and hemp, as well as cellulose and regenerated cellulose. Preferred suitable textile fibre materials are made of cotton.

The 2,4-bis(alkylamino)pyrimidines according to the invention are also suitable for the treatment of plastics, especially for imparting antimicrobial properties to or preserving plastics, e.g. polyethylene, polypropylene, polyurethane, polyester, polyamide, polycarbonate, latex etc. Fields of use therefor are, for example, floor coverings, plastics coatings, plastics container and packaging materials; kitchen and bathroom utensils (e.g. brushes, shower curtains; sponges, bathmats), latex, filter materials (air and water filters), plastics articles used in the field of medicine, e.g. dressing materials, syringes, catheters etc., so-called “medical devices”, gloves and mattresses.

Paper, for example papers used for hygiene purposes, may also be provided with anti-microbial properties using the 2,4-bis(alkylamino)pyrimidines of formula (1) according to the invention.

It is also possible for nonwovens, e.g. nappies/diapers, sanitary towels, panty liners, and cloths for hygiene and household uses, to be provided with antimicrobial properties in accordance with the invention.

The 2,4-bis(alkylamino)pyrimidines of formula (1) are also used in washing and cleaning formulations, e.g. in liquid and powder washing agents or softeners.

The 2,4-bis(alkylamino)pyrimidines of formula (1) may especially also be used in household and all-purpose cleaners for cleaning and disinfecting hard surfaces.

A cleaning preparation has, for example, the following composition:

-   0.01 to 5% by weight of a compound of formula (1) -   3.0% by weight octyl alcohol 4EO -   1.3% by weight fatty alcohol C₈-C₁₀polyglucoside -   3.0% by weight isopropanol -   ad 100% by weight water.

In addition to preserving cosmetic and household products, the preservation of technical products, the provision of technical products with antimicrobial properties and use as a biocide in technical processes are also possible, for example in paper treatment, especially in paper treatment liquors, in printing ink thickeners consisting of starch or of cellulose derivatives, in surface-coating compositions and in paints.

The 2,4-bis(alkylamino)pyrimidines of formula (1) are also suitable for the antimicrobial treatment of wood and for the antimicrobial treatment of leather, the antimicrobial preservation of leather and the provision of leather with antimicrobial properties.

The compounds according to the invention are also suitable for the protection of cosmetic products and household products from microbial spoilage.

In addition to their generally antimicrobial action, the 2,4-bis(alkylamino)pyrimidines of formula (1) according to the invention are moreover capable of penetrating bioflims on living and non-living surfaces, of preventing the adhesion of bacteria to surfaces and any further build-up of the bioflim, of detaching such biofilm and/or inhibiting the further growth of the biofilm-forming micro-ogranisms in the biological matrix, or of killing such micro-organisms.

Biofilms are understood, very generally, to be aggregations of living and dead micro-organisms, especially bacteria, that adhere to living and non-living surfaces, together with their metabolites in the form of extracellular polymeric substances (EPS matrix), e.g. polysaccharides. The activity of antimicrobial substances that normally exhibit a pronounced growth-inhibiting or lethal action with respect to planktonic cells may be greatly reduced with respect to microorganisms that are organised in bioflims, for example because of inadequate penetration of the active substance into the biological matrix.

In the present invention, this relates, very especially, to bioflims on human tooth surfaces and oral mucosa, which play a crucial role in the onset of degenerative diseases in the oral cavity, e.g. caries or periodontitis, as a result of the biofilm-forming micro-organisms or their metabolites.

The following Examples illustrate, but do not limit, the present invention.

IMPLEMENTATION EXAMPLES Example 1 Preparation of N,N′-bis(2A-dioctylamino-6-methyliprimidine (PY5)

8.15 g of 2,4-dichloro-6-methyl-pyrimidine (50 mmol) are heated with 19.39 g of octylamine (150 mmol) and 20.73 g of potassium carbonate (150 mmol) in 20 ml of dioxane for 16 hours at 100° C. After cooling, the product is taken up in 300 ml of ethyl acetate and washed with 0.5 mol/liter of sodium hydroxide solution and saturated sodium chloride solution. The product is concentrated in vacuo and then octylamine is distilled off for 2 hours at 140° C. under a rotary slide valve vacuum. 12.95 g of N,N′-bis(2,4-dioctylamino)-6-methylpyrimidine (37.15 mmol, 74.3% of theory) are obtained. The end product is analysed by NMR, HPLC-MS, GC and HPLC.

GC: 98% area

M+1=349

NMR (¹H in DMSO): 0.85, t, 6H; 1.25, m, 20H; 1.5, m, 4H; 2, s, 3H; 4.2, m, 4H; 5.5, s, 1H; 6.2, s, 1H; 6.6; s, 1H.

Example 2 Preparation of N,N′-bis(2.4-dibenzylamino)-6-methylpyrimidine (PY8)

8.15 g of 2,4-dichloro-methyl-pyrimidine (50 mmol) are heated with 16 g of benzylamine (150 mmol) and 20.73 g of potassium carbonate (150 mmol) in 20 ml of dioxane for 16 hours at 100° C. After cooling, the product is taken up in 300 ml of ethyl acetate and washed with 0.5 mol/liter of sodium hydroxide solution and saturated sodium chloride solution. The product is concentrated in vacuo and then benzylamine is distilled off for 2 hours at from 105 to 120° C. under a rotary slide valve vacuum, and the product is recrystallised from isopropanol. N,N′-Bis(2,4-dibenzylamino)-6-methylpyrimidine is obtained in a yield of 76%. Purity: GC 100% NMR (¹H in DMSO, ppm): 2, s, 3H; 4.45, m, 4H; 5.6, s, 1H; 6.95, s, 1H; 7.25, m, 11H.

Example 3 Preparation of N,N′-bis(2.4-diphenylethylamino)-6-methylpyrimidine (PY9)

8.15 g of 2,4-dichloro-6-methyl-pyrimidine (50 mmol) are heated with 18.17 g of phenyl-ethylamine (150 mmol) and 20.73 g of potassium carbonate (150 mmol) in 20 ml of dioxane for 16 hours at 100° C. After cooling, the product is taken up in 300 ml of ethyl acetate and washed with 0.5 mol/liter of sodium hydroxide solution and saturated sodium chloride solution. The product is concentrated in vacuo and then phenylethylamine is distilled off for 2 hours at 150° C. under a rotary slide valve vacuum and the product is recrystallised from isopropanol. N,N′-Bis(2,4-diphenylethylamino)-6-methylpyrimidine is obtained in a yield of 98%.

Purity: GC 100% HPLC 98%

NMR (¹H in DMSO, ppm): 2, s, 3H; 2.9, t, 4H; 3.45, m, 4H; 5.6, s, 1H; 6.45, s, 1H; 6.8, s, 1H; 7.25, m, 10H.

Example 4 Preparation of 4-hydroxy-2-phenylamino-6-phenylpyrimidine

7 g (20 mmol) of phenylguanidine carbonate are reacted in 5 ml of absolute ethanol with 27.2 g (80 mmol) of a 20% sodium ethanolate solution. 11.5 g of ethylbenzoyl acetate (59.8 mmol) are added dropwise thereto in the course of 15 minutes at 75° C. The reaction mass is then stirred for 15 hours at 70° C. and, after cooling, is extracted with 50 ml of di-chloromethane and washed three times with 40 ml of water/3 ml of acetic acid.

The organic phase is dried over sodium sulfate and concentrated by evaporation.

5.86 g (55.7% of theory) of 4-hydroxy-2-phenylamino-6-phenylpyrimidine are obtained.

NMR (¹H in DMSO, ppm): 6.45, s, 1H; 7.05, t, 1H; 7.4, t, 2H; 7.5, m, 3H; 7.75, d, 2H; 8, m, 2H; 9, s, 11H; 11.05, s, 1H.

Example 5 Preparation of 4-chloro-2-phenylamino-6-phenylpyrimidine

2 g (7.6 mmol) are reacted in 10 ml of toluene with 3.5 g of phosphorus oxychloride. The reaction mass is heated to 80° C and 1.53 g of triethylamine (15.1 mmol) are added dropwise thereto in the course of 20 minutes. After a reaction time of 2 hours at 80° C., the mass is cooled in an ice bath and 28 ml of 4M sodium hydroxide solution are added dropwise thereto.

The aqueous phase is extracted three times with ethyl acetate.

After concentration of the organic phase by evaporation, 2.12 g (99.1% of theory) of 4-chloro-2-phenyl-amino-6-phenylpyrimidine are obtained.

NMR (¹H in DMSO, ppm): 7, t, 11H; 7.3, t, 2H; 7.55, m, 4H; 7.8, d, 2H; 8.2, m, 2H; 10.05, s, 11H.

Example 6 Reaction of 4-chloro-2-phenylamino-6-phenylpyrimidine with amines

The reactions are carried out in parallel robotically.

56.3 mg of 4-chloro-2-phenylamino-6-phenylpyrimidine (0.2 mmol) are dissolved in 0.5 ml of dioxane. 38.7 mg of diisopropylamine (0.3 mmol) and 3 mmol of amine are added thereto and the reaction mixture is heated at 85° C. for 21 hours. After cooling, the mass is extracted with 2 ml of dichloromethane and washed three times with 1.125 ml of acetic add (13% in water) and 1.2 ml of sodium hydroxide solution.

The organic phases are dried and lyophillsed.

The compounds (PY10)-(PY29) (see Table 1) are prepared according to this method. They were analysed by LC-MS.

Example 7 Preparation of the Compound of Formula C

34.65 g of octylguanidine acetate A (0.15 mol) are reacted in 30 ml of ethanol with 102 g of 20% sodium ethanolate solution in ethanol (0.3 mol). The reaction mixture is heated to 75° C., and 26.15 g of methyl acetate B (0.22 mol) are added thereto in the course of one hour, and the mixture is stirred for 12 hours. After cooling, the reaction mass is diluted with dichloro-methane and washed three times with water/acetic add and twice with sodium hydroxide solution. The combined alkaline aqueous phases are adjusted to pH 6 with acetic acid and extracted with dichloromethane, dried over sodium sulfate and concentrated by evaporation.

30.74 g of compound C (87% of theory) are obtained.

Purity in HPLC: 99%

NMR (in CD₂Cl₂ in ppm): 0.9, t, 3H; 1.3, m, 10H; 1.6, qt, 2H; 2.2, s, 3H; 3.35, m, 2H; 5.6, s, 1H; 6.7, s, 1H.

Example 8 Preparation of the Compound of Formula D

18.96 g (0.08 mol) of the compound of formula C are reacted in 60 ml of toluene with 36.85 g of phosphorus oxychloride. The reaction mass is heated to 80° C. After a reaction time of 2 hours at 80° C., the mass is cooled in an Ice bath and 4M sodium hydroxide solution is added dropwise thereto. The aqueous phase is extracted three times with toluene.

After concentration of the organic phase by evaporation, 20.04 g (98% of theory) of the compound of formula D are obtained.

Purity in GC: 100%

NMR (in CD₂Cl₂ in ppm): 0.8, t, 3H; 1.3, m, 10H; 1.55, qt, 2H; 2.2, s, 3H; 3.3, q, 2H; 5.25, a, 1H; 6.35, s, 1H.

Example 9 Preparation of the Compound of Formula PY44

12.96 g of compound D (0.048 mol) are mixed with 6.19 g of di-isopropylamine (0.048 mol) in 60 ml of dioxane and heated at reflux. 4.9 g of pyrrolidine (0.057 mol) are added dropwise thereto in the course of 25 minutes and the reaction mixture is stirred at reflux for 29 hours. After cooling, the reaction mass is diluted with dichloromethane and washed three times with water/acetic acid and twice with sodium hydroxide solution. The organic phase is dried over sodium sulfate and concentrated by evaporation. 12.73 g of compound PY44 (91.4% of theory) are obtained.

Purity in GC: 100%

NMR (CD₂Cl₂ in ppm): 0.8, t, 3H; 1.2, m, 10H; 1.45, qt, 2H; 1.85, m, 4H; 2, s, 3H; 3.2-3.3, m (2 signals), 6H; 4.7, s, 1H; 5.45, s, 1H.

Example 10 Preparation of the Compound of Formula F

18.48 g of octylguanidine acetate A (0.08 mol) are reacted in 15 ml of ethanol with 54.4 g of 20% sodium ethanolate solution in ethanol (0.16 mol). The reaction mixture is then heated to 75° C and 24 g of methyl 2-hexylacetoacetate E (0.12 mol) are added thereto in the course of 30 minutes, and the mixture is stirred overnight. After cooling, the reaction mass is diluted with dichloromethane and washed twice with water/acetic acid. The organic phase is dried over sodium sulfate and concentrated by evaporation. The crude product is recrystallised from acetone. 14.86 g of compound F (57.9% of theory) are obtained.

LC-MS: a compound having M=321.

Example 11 Preparation of the Compound of Formula G

13.16 g (0.041 mol) of a compound of formula F are reacted in 40 ml of toluene with 18.89 g of phosphorus oxychloride. The reaction mass is heated to 80° C. After a reaction time of 2 hours at 80° C., the mass is cooled in an ice bath and 4M sodium hydroxide solution is added dropwise thereto. The aqueous phase is extracted three times with toluene.

After concentration of the organic phase by evaporation, 13.65 g (98% of theory) of the compound of formula G are obtained.

Purity in GC: 100%

NMR (CD₂Cl₂ in ppm): 0.9, m, 6H; 1.3, m, 18H; 1.5, m, 2H; 1.6, m, 2H; 2.4, s, 3H; 2.6, t, 2H; 3.4, q, 2H; 5.6, s, 1H.

Example 12 Preparation of the Compound of Formula PY55

11.88 g of compound G (0.035 mol) are stirred with 51.87 g of 1,8-diamino-3,6-dioxaoctane (0.35 mol) and 6.77 g of diisopropylamine (0.0525 mol) at 110° C. for 23 hours. After cooling, the reaction mass is diluted with dichloromethane and washed three times with water and twice with water/acetic acid. The combined aqueous phases are adjusted to pH 9 with sodium hydroxide solution and extracted with dichloromethane, dried over sodium sulfate and concentrated by evaporation. 14.45 g of compound PY55 (64.6% of theory) are obtained.

Purity in GC: 100%

NMR (CD₂Cl₂ in ppm): 0.9, m, 6H; 1.3, m, 20H; 1.55, m, 2H; 2.15, s, 3H; 2.3, t, 2H; 2.4, s, 2H; 2.8, t, 2H; 3.3, q, 2H; 3.45, t, 2H; 3.6, m, 8H; 5.1, s, 1H; 5.7, s, 1H.

Example 13 Determination of the Minimum Inhibiting Concentration (MIC value) in Microtiter Plates

Nutrient Medium:

Casein/soybean flour peptone bouillon for the preparation of the precultures of the test bacteria and yeast.

Examples of Test Organisms:

-   -   Bacteria: Staphylococcus aureus ATCC 6583         -   Corynebacterium xerosis ATCC 373 (a)         -   Actinomyces viscosus ATTC 43146         -   Escherichia Coli ATTC 10536             Procedure:

The test substances are predissolved in dimethyl sulfoxide (DMSO) and tested in a serial dilution of 1:2.

Bacteria and yeast are cultured overnight in CASO bouillon.

All test organism suspensions are adjusted to an organism count of 1-5×10⁸ CFU/ml with 0.85% sodium chloride solution.

The test substances are prepipetted into microtiter plates in an amount of 8 μl per well.

The previously adjusted organism suspensions are diluted 1:100 in CASO bouillon and added to the test substances in an amount of 192 μl per well.

The test batches are incubated for 48 hours at 37° C.

After incubation, the growth is determined by reference to the turbidity of the test batches (optical density) at 620 nm in a microplate reader.

The minimum inhibiting concentration (MIC value) is the concentration of substance at which (compared with the growth control) an appreciable inhibition of the growth (≲20% growth) of the test organisms is ascertained.

Three microtiter plates are used for each test organism and substance concentration.

Table 2 shows the microbiological test results:

TABLE 2 Determination of the minimum inhibiting concentration in microtitre plates Compound of formula MIC sa MIC ec MIC cx MIC av (PY1) 11 >120 6 6 (PY2) 105 >120 <3.75 26 (PY3) 43 >120 11 11 (PY4) 79 >120 20 20 (PY5) <3.75 >120 <3.75 <3.75 (PY6) 51 >120 13 51 (PY7) 32 >120 4 8 (PY8) 17 34 8 8 (PY9) 5 37 <3.75 <3.75 (PY10) 8 >120 <3.75 (PY11) 25 >120 <3.75 (PY12) 32 64 <3.75 (PY13) 9 >120 <3.75 (PY14) 58 116 29 (PY15) 15 >120 7 (PY16) 37 >120 <3.75 (PY17) 4 >120 <3.75 (PY18) <3.75 >120 <3.75 (PY19) 32 8 8 (PY20) 29 29 15 (PY21) <3.75 >120 <3.75 (PY22) 40 >120 20 (PY23) 160 >120 40 (PY24) >120 >120 16 (PY25) 76 >120 10 (PY26) >120 >120 15 (PY27) >120 >120 60 (PY28) 40 160 10 (PY29) 10 >120 <3.75 PY30 16.5 >120 16.5 8.25 PY31 <3.75 >120 <3.75 <3.75 PY32 19.5 >120 <3.75 <3.75 PY33 <3.75 9.75 <3.75 <3.75 PY34 8 >120 <3.75 <3.75 PY35 17 34 8.5 8.5 PY36 <3.75 >120 <3.75 <3.75 PY37 <3.75 >120 <3.75 <3.75 PY38 33 66 8.25 8.25 PY39 <3.75 >120 <3.75 <3.75 PY40 9 >120 <3.75 <3.75 PY41 64 >120 64 64 PY42 <3.75 >120 <3.75 <3.75 PY43 27 54 13.5 6.75 PY44 <3.75 30 <3.75 <3.75 PY45 <3.75 58 <3.75 <3.75 PY46 7.25 >120 <3.75 <3.75 PY47 <3.75 35 <3.75 <3.75 PY48 32 128 8 8 PY49 64 >120 32 16 PY50 64 64 32 16 PY51 >120 >120 <3.75 <3.75 PY52 9.25 9.25 <3.75 <3.75 PY53 108 >120 <3.75 <3.75 PY54 <3.75 36 <3.75 <3.75 PY55 <3.75 <3.75 <3.75 <3.75 PY56 18.5 9.25 <3.75 <3.75 PY57 9.5 >120 <3.75 <3.75 PY58 17 >120 <3.75 <3.75 PY59 19.5 >120 9.75 9.75 PY60 27 >120 13.5 6.75 PY61 18.5 >120 9.25 9.25 PY62 76 >120 19 9.5 PY63 8.75 >120 <3.75 <3.75 PY64 36 >120 <3.75 <3.75 PY65 <3.75 <3.75 <3.75 <3.75 PY66 <3.75 >120 <3.75 7 PY67 <3.75 >120 <3.75 <3.75 PY68 6.25 >120 <3.75 <3.75 PY69 <3.75 >120 <3.75 <3.75 PY70 31 >120 <3.75 <3.75 PY71 9 >120 <3.75 <3.75 PY72 31 15.5 <3.75 <3.75 PY73 18 18 <3.75 <3.75 PY74 34 >120 8.5 8.5

Example 14 Determination of the Minimum Inhibiting Concentration MIC [ppm] of a Broadened Organism Spectrum

-   Medium: Casein/soybean flour peptone agar (Merck)     -   *Sabouraud 4% glucose agar (Merck) -   Dilution medium: sterile 0.85% NaCl solution -   Test organisms: Staphylococcus aureus ATCC 6853 and 9144     -   Staphylococcus epidermidis ATCC 12228     -   C. xerosis ATCC 373 **     -   C. minutissimum ATCC 23348     -   Proplonibacterium acnes ATCC 6919     -   Escherichia coli ATCC 10536 and NCTC 8196     -   Proteus vulgaris ATCC 6896     -   Klebsiella pneumoniae ATCC 4352     -   Salmonella choleraesuis ATCC 9184     -   Pseudomonas aeruginosa ATCC 15442     -   *Candida albicans ATCC 10231     -   *Aspergillus niger ATCC 6275 -   Incubation: 24 hours at 37° C.     -   *3 days at 28° C. -   Test solution: 1% stock solutions of all the test substances in a     suitable solvent are prepared and diluted in serial dilutions (1:10,     1:100 and 1:1000 dilution), where possible diluted to such an extent     that the end concentrations in agar are from 500 ppm to 10 ppm.     Test principle:

0.3 ml of the dilution stage in question is mixed with 15 ml of still-liquid nutrient medium.

When the nutrient substrate has solidified, 10 μl portions of a suitable organism dilution of the test strains in 0.85% NaCl solution are spotted onto the agar medium:

TABLE 3 Determination of the minimum inhibiting concentration MIC [ppm] of a broadened organism spectrum Compound of formula Microorganism (PY5) (PY8) (PY9) Staphylococcus aureus ATCC 6538 3.91 31.25 7.8 Staphylococcus aureus ATCC 9144 3.91 31.25 7.8 Staphylococcus epidermidis ATCC 12228 3.91 31.25 7.8 C. xerosis ATCC 373** 7.81 7.8 1.95 C. minutissimum ATCC 23348 3.91 15.63 3.9 Propionibacterium acnes ATCC 6919*** 3.91 31.25 7.8 Escherichia coli NCTC 8196 >1000 31.25 15.63 Escherichia coli ATCC 10536 >1000 62.5 250 Proteus vulgaris ATCC 6896 >1000 >500 >500 Klebsiella pneumoniae ATCC 4352 250 15.63 7.8 Salmonella choleraesuis ATCC 9184 >1000 62.5 250 Pseudomonas aeruginosa ATCC 15442 >1000 >500 >500 Candida albicans ATCC 10231 >1000 250 62.5 Aspergillus niger ATCC 6275 >1000 250 250

TABLE 3a Determination of the minimum inhibiting concentration MIC°[ppm] of a broadened organism spectrum Microorganisms (PY44) (PY55) Staphylococcus aureus ATCC 6538 7.8 7.8 Staphylococcus aureus ATCC 9144 7.8 3.9 Staphylococcus epidermidis ATCC 12228 3.9 7.8 C. xerosis ATCC 373** 3.9 3.9 C. minutissimum ATCC 23348** 3.9 3.9 Propionibacterium acnes ATCC 6919*** 3.9 3.9 Escherichia coli NCTC 8196 15.63 7.8 Escherichia coli ATCC 10536 62.5 7.8* Proteus vulgaris ATCC 6896 >500 >500 Klebsiella pneumoniae ATCC 4352 7.8 15.63 Salmonella choleraesuis ATCC 9184 62.5 7.8 Pseudomonas aeruginosa ATCC 15442 >500 >500 Candida albicans ATCC 10231 250 125 Aspergillus niger ATCC 6275 500 500 *very slow growth, no growth in the next dilution stage **3 days incubation, ***3 days incubation under anaerobic conditions

Example 15 Determination of the Minimum Inhibiting Concentration MIC (ppm) of a Broadened Organism Spectrum: Oral Organisms

-   Medium: thioglycolate bouillon with hemin and menadione Columbia     bouillon with hemin and menadione for P. gingivalis and P.     nigrescens -   Dilution medium: the appropriate amount of the substances was     pipetted directly into the medium. -   Test organisms: Actinobacillus actinomycetemcomitans ATCC 43718     -   Streptococcus gordonil ATCC 10558     -   Streptococcus mutans ATCC 33402     -   Actinomyces viscosus ATCC 43146     -   Fusobacterium nucleatum subsp. polymorphum ATCC 10953     -   Porphyromonas gingivalis ATCC 33277     -   Prevotella nigrescens ATCC 33563 -   Incubation: 7-10 days at 37° C anaerobic, or 24 hours aerobic with     10% CO₂ for Streptococci and A. actinomycetemcomitans -   Test solution: Stock solutions of all the test substances in ethanol     at 1500 ppm (w/w) are used.     Test Principle:

Bacteria are removed from blood agar plates using cotton wool buds and a suitable optical density (McFarland 0.5) is adjusted in an appropriate medium; that solution is used undiluted for F. nucleatum and P. nigrescens, and in a dilution of 1:20 for the other strains. 0.1 ml of bacterial culture is added per 2 ml of active ingredient solution and incubation is carried out as described above.

TABLE 4 Determination of the minimum inhibiting concentration MIC [ppm] of a broadened organism spectrum: oral organisms Compound of formula Microorganism (PY5) (PY8) (PY9) A. actinomycetemcomitans ATCC43718 >15 >15 >15 S. gordonii ATCC 10558 15 >15 15 S. mutans ATCC 33402 3.75 >15 15 A. viscosus ATCC 43146 3.75 3.75 3.75 F. nucleatum subsp. Polymorphum >15 15 15 ATCC 10953 P. gingivalis ATCC 3277 7.5 15 7.5 P. nigrescens ATCC 33563 15 15 7.5 Microorganism (PY44) (PY55) A. actinomycetemcomitans ATCC 43718 >15 15 S. gordonii ATCC 10558 7.5 3.8 S. mutans ATCC 33402 7.5 7.5 A. viscosus ATCC 43146 3.8 3.8 F. nucleatum subsp. polymorphum 3.8 7.5 ATCC 10953 P. gingivalis ATCC 3277 3.8 3.8 P. nigrescens ATCC 33563 3.8 3.8 

1. A method for the antimicrobial treatment of a surface of a plastic, which method comprises contacting said surface of a plastic with a surface coating composition containing an antimicrobially effective amount of a 2,4-bis(alkylamino)pyrimidine of formula

wherein R₁ is methyl, R₂ is hydrogen, R₃ is hydrogen, R₄ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl and R₅ and R₆ together form a pyrrolidine, piperidine or morpholine ring; or R₁ is methyl, R₂ is hydrogen, R₃ and R₄ together form a pyrrolidine, piperidine or morpholine ring, R₅ is hydrogen and R₆ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl; or R₁ is methyl, R₂ is straight chain C₃-C₈alkyl, R₃ and R₅ are hydrogen, R₄ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl and R₆ is di-C₁-C₆alkylamino-C₁-C₆alkyl, mono-C₁-C₆alkylamino-C₁-C₆alkyl, or —(CH₂)₂—(O—(CH₂)₂)₁₋₂—NH₂.
 2. A method according to claim 1 wherein R₁ is methyl, R₂ is hydrogen, R₃ is hydrogen, R₄ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl and R₅ and R₆ together form a pyrrolidine, piperidine or morpholine ring; or R₁ is methyl, R₂ is hydrogen, R₃ and R₄ together form a pyrrolidine, piperidine or morpholine ring, R₅ is hydrogen and R₆ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl.
 3. A method according to claim 2 wherein R₁ is methyl, R₂ is hydrogen, R₃ is hydrogen, R₄ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl and R₅ and R₆ together form a pyrrolidine; or R₁ is methyl, R₂ is hydrogen, R₃ and R₄ together form a pyrrolidine, R₅ is hydrogen and R₆ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl.
 4. A method according to claim 2 wherein R₁ is methyl, R₂ is hydrogen, R₃ is hydrogen, R₄ is hexyl, heptyl, octyl, nonyl or decyl and R₅ and R₆ together form a pyrrolidine, piperidine or morpholine ring; or R₁ is methyl, R₂ is hydrogen, R₃ and R₄ together form a pyrrolidine, piperidine or morpholine ring, R₅ is hydrogen and R₆ is hexyl, heptyl, octyl, nonyl or decyl.
 5. A method according to claim 4 wherein R₁ is methyl, R₂ is hydrogen, R₃ is hydrogen, R₄ is hexyl, heptyl, octyl, nonyl or decyl and R₅ and R₆ together form a pyrrolidine ring; or R₁ is methyl, R₂ is hydrogen, R₃ and R₄ together form a pyrrolidine, R₅ is hydrogen and R₆ is hexyl, heptyl, octyl, nonyl or decyl.
 6. A method according to claim 5 wherein R₁is methyl, R₂is hydrogen, R₃is hydrogen, R₄is octyl and R₅ and R₆ together form a pyrrolidine ring; or R₁ is methyl, R₂ is hydrogen, R₃ and R₄ together form a pyrrolidine, R₅ is hydrogen and R₆ is octyl.
 7. A method according to claim 1 wherein R₁ is methyl, R₂ straight chain C₃-C₈alkyl, R₃ and R₅ are hydrogen, R₄ is butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl R₆ is di-C₁-C₆alkylamino-C₁-C₆alkyl, mono-C₁-C₆alkylamino-C₁-C₆alkyl, or —(CH₂)₂—(O—(C₂)₂)₁₋₂—NH₂.
 8. A method according to claim 7 wherein R₆ is —(C₂)₂—(O—(CH₂)₂)₁₋₂—NH₂.
 9. A method according to claim 7 wherein R₄ is hexyl, heptyl, octyl, nonyl, decyl.
 10. A method according to claim 8 wherein R₄ is hexyl, heptyl, octyl, nonyl, decyl.
 11. A method according to claim 8 wherein R₂ is hexyl and R₄ is octyl. 